In disc drives, one or more sliders are provided that support read/write heads that fly over a moving disc storage surface. Each slider includes an air bearing surface that faces a moving disc surface and that interacts aerodynamically with a moving layer of air adjacent the moving disc surface. The aerodynamic interaction generates a force on the slider. The slider is suspended from a load beam that exerts a suspension load force on the slider. The air bearing surface is shaped such that the aerodynamic force and the suspension load force are in a delicate balance that controls a fly height for the slider in a narrow range needed for optimum read/write performance. If this delicate balance is upset, the slider may crash into the moving disc storage surface. The slider is also highly miniaturized to have a low mass so that it adjust fly height rapidly in response to changes in the aerodynamic force so that the slider does not crash into the moving disc surface.
Electrical interconnections between the read/write head and read/write conditioning circuitry are made by way of flexible circuits so that mechanical forces from the interconnections are low and do not upset the delicate balance of forces on the low mass slider.
In some cases, conditioning circuitry for the read/write head is supported at a location that is remote from the slider and read/write head. The mass of conditioning circuit integrated circuit package is mechanically decoupled from the slider and does not add a large suspended mass and slow down the mechanical response of the slider to changing aerodynamic forces. Integrated conditioning circuitry is typically mounted on a circuit board, or in some cases in an integrated circuit package on a portion of the flexible interconnect circuit. The mass of the conditioning circuitry is large relative to the mass of the slider. The mass of the conditioning circuitry is mechanically decoupled from the mass of the slider and read/write head.
In other cases, actively powered conditioning circuitry is fabricated as part of the same substrate that includes the head. In this arrangement, there is a problem with power dissipated in the conditioning circuitry heating the substrate and overheating the head. In this arrangement integrated circuit processing can be highly complex when optimal performance of the head requires one crystallographic orientation of the substrate, and optimal performance of the conditioning circuitry requires a different crystallographic orientation of the substrate. Processing technology for forming the head can be markedly different that processing technology for the conditioning circuitry, leading to a large number of steps needed to fully fabricate a substrate with both a head and a conditioning circuit.
The read/write data rates of data storage devices, however, are increasing. On the one hand, the power consumption for heads is decreasing in newer designs of data storage devices. On the other hand, conditioning circuitry for newer design heads is becoming more complex and dissipating more power. In newer designs, the heads transduce lower power, higher frequency electrical signals that are excessively loaded by the flexible electrical interconnections that extend between the read/write heads and the conditioning integrated circuitry. The electrical loading degrades the read/write signals, causes impedance matching and reflection problems, and reduces noise margins. The flexible circuit interconnection between the read/write head and the conditioning circuitry sets an undesirable limit on the read/write data speeds in new disc drive designs.
There is a desire to move conditioning circuitry close to the head, however, power consumption and complex process technologies make placement of conditioning circuitry directly on the head increasingly impractical.
A method and an apparatus are needed to overcome the problem of electrical loading of interconnect circuitry between read/write heads and conditioning circuitry without unduly degrading the mechanical responsiveness of the low mass mechanical suspension of the slider and without overheating the head with heat from the conditioning circuitry. Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.